THE FLOW OF WATER IN DRAIN TILE. 

 NOMENCLATURE. 



The following symbols are used throughout this report: 



rf=mean depth of flow in the drain, in feet. 

 D=mean inside diameter of the tile, in feet. 



r=mean inside radius of the tile, in feet=J D. 



Q=mean discharge of the tile during the test, in second-feet. 

 ^4=mean area of the tile bore, in square feet=7rr 2 . 



a=average area of flow in the tile, in square feet. 



Q 



F=mean velocity of the water during the test in feet per second =— 

 P=wetted perimeter in the tile, in feet. 



a . I) 



i?=mean hydraulic radius=-p - , in a tile drain running full i?=^r- 



s=hydraulic grade or slope. 

 n=coefficient of roughness in Kutter's formula. 

 C= coefficient in Chezy's velocity formula. 

 C w = coefficient in the Williams-Hazen velocity formula. 

 ft=total difference in elevation between ends of a main drain, in feet. 

 Z=length of the drain tested, in feet. 



6=summation of the amounts of excess head in the submains, in feet. 

 T= number of submains. 

 Z7=depth of the soil over the main drain at its head, in feet; used only when 



main drains are 1,000 feet or more in length. 

 s=mvz is the general equation for the flow of water in drain tile, in which z 



is always constant and m varies only with the size of trie. 

 m=eDx is the equation for the variation of m for a series of drain tile of various 



sizes but of the same material; e and x are constants. 

 m / =the special values of m found for each series of tile. 



Whenever a test is numbered, the reference is to the correspond- 

 ing numbers in Tables 3 and 4 and to Plates X and XI. 



Throughout this discussion the term " concrete tile" is used 

 instead of "cement tile." The American Society for Testing Mate- 

 rials, in its standard specifications for drain tile, defines concrete 

 tile as tile made of "a suitable mixture of Portland cement, mineral 

 aggregates, and water, hardened by hydraulic chemical reaction." 



FORMULAE FOR FLOW OF WATER IN DRAIN TILE. 



It is common knowledge that the water enters drains at the joints 

 and not through the walls of the tile. Since there is a joint either 

 every foot or every 2 feet in the length* of the drain, water enters the 

 tile drain throughout its entire length. In tile of small sizes, this 

 leads to an appreciable variation in the amount of water carried 

 at different points in the tile; but in the larger sizes the amount 

 entering is so small a proportion of the amount carried as to be 

 unimportant in considering carrying capacity. 



The water in any tile drain is caused to flow and velocity is set 

 up by two forces, one due to the grade of the tile line, and the other 

 created when there is a variation in areas of water cross-section. 



